Ensuring that temporary structures projects are managed well so that budgets are maintained and safety is ensured throughout the project is the objective of this chapter. The chapter presents recommendations for the quality control, quality assurance and quality improvement processes to be undertaken in the design, assembly, use and maintenance of the temporary structures to reduce the associated risks. The chapter starts by discussing the importance of having clear management structures for projects involving collaboration between the client, designer and the construction engineer. This leads to the importance of an overall project supervisor, sometimes called a Temporary Works Controller, who has ultimate authority for the safe execution of the project. The use of Structural Health Monitoring is described with particular reference to its ability to make the erection of temporary structures projects safer.
Top8.1 Introduction
Temporary structures have a major role in the execution time, cost, quality, durability, safety, efficiency, utility and aesthetics of any construction project. Therefore, it is not surprising that a correct choice, good planning, designing and operation of temporary structures are keys for the success of every construction project. In order to achieve a successful project, continuous knowledge exchange and synchronised planning between the permanent structure designer, the project contractor, the temporary structures designer, the temporary structures sub-contractor and others must exist, see Figure 1 for example.
Unfortunately this is not always a reality. As so clearly demonstrated in Chapter 7, poor project management is often a cause of temporary structures collapses. For example, Milojkovic (1999) demonstrated that a simple domestic scaffold under conditions of poor design and erection even if with good site management, could exhibit a global safety factor of just above unity, whereas the same scaffold under good design, erection and site management should have a global safety factor of approximately ten. Even more importantly, it was found that with poor site management, regardless of the quality of design, the maximum value of the global safety factor was not larger than unity. This implies that the structure would be on the verge of collapse at all times and any sources of inadequate design or improper erection would cause collapse. See Tables 1 to 3 of Chapter 7 for the details.
While recognising that nature of things is ultimately to fail, the focus of efforts should be in ensuring that the risk level of the latter occurring is acceptable during the planned design working life of structures. Of course, it is not possible to know exactly if failure will occur in the future. As a result, there are large uncertainty levels and complexities involved in developing plans for the future. In this context, decisions tend to be short-term intended: regulatory authorities may be reluctant to impose more severe requirements to legal documents, investments focus more on replacing and renewing as needed rather than modernising infrastructure and expenditure takes place in response to a crisis rather than proactively planning and managing infrastructure assets such as temporary structures. In addition, the mainstream overarching management objective has been to operate infrastructure systems at near maximum capacity. This, however, causes systems to be less resilient against anticipated or unknown hazards during the systems lifespan; optimisation for one set of conditions creates vulnerabilities to changes in those conditions. One should always consider that “failure is inevitable, the question is when”.
The economic risk from natural or man-made causes perceived by stakeholders often represents a small percentage of the capital at risk. This might be often the case, but does not take fully into consideration the follow-up consequences, e.g. loss of life, very high economic losses when compared with potential investment costs, and impacts on GDP due to disruption of service, reputational damage, contractual penalties and the potential for litigation (Guthrie & Konaris, 2012).
Quality is defined in ISO 9000 as the degree to which a set of inherent characteristics of an object fulfils a need or expectation that is stated, generally implied or obligatory (ISO, 2015). In the latter definition, “object” means “anything perceivable or conceivable” (ISO, 2015). Quality management can include establishing quality policies and quality objectives, and processes to achieve these quality objectives through quality planning, quality assurance, quality control, and quality improvement (ISO, 2015).
Figure 1. Activities and responsibilities in falsework design and construction for standard (top) and special (bottom) projects recommended in CIP (2011). ©2016 Construction Industry Publications. Used with permission
The definition of Quality Assurance (QA) is defined to be those activities which are focused on providing confidence that the quality requirements will be fulfilled. It focuses on ensuring that defects are prevented and that potential defects in new products or processes are eliminated. It requires regular audits of performance and good quality management producing high quality documentation at all stages.